Organic electroluminescent devices have a lot of excellent properties such as self-luminescence, high-brightness, broad view angle, high contrast, low energy consumption, rapid response, broad range of operation temperature, high luminescent efficiency, simple process for manufacture, and so on, so that they arrest many attentions around the world.
Currently, electrode leads of an organic electroluminescent device are usually made on an electroluminescent substrate, whatever the electrode leads are disposed at one side, two sides or four sides of the substrate, so that the frame size of display module increases and the luminescent area is reduced, and this problem become more serious with the increase of pixel number, as shown in FIG. 1. FIG. 2 is a structural schematic view for bonding and packaging an organic electroluminescent device in the prior art, in which a lead region 22 surrounds a substrate 21, an organic electroluminescent device is packaged between a packaging sheet 23 and the substrate 21 by using a packaging adhesive, the packaging sheet usually has an area less than the area of the substrate, a packaging region 24 and a light emitting region 25 are also presented, and it can be seen from FIG. 2 that the area of light emitting region of such a conventional organic electroluminescent device is significantly reduced due to the existence of the lead region.
In a double-sided organic electroluminescent device module of the art, the bonding of leads is also performed on substrate, a packaging sheet is sandwiched between two light-emitting components for packaging, supporting drying and heat dispersion, so that such a device has a relatively large volume and a relatively broad frame after bonding, and is difficult in cutting procedure. For example, China Patent Application Series No. 200510048837.4, published on Aug. 23, 2006 discloses a double-sided organic electroluminescent device in which a supporter is disposed between two electroluminescent components, the supporter is used to package the device, and a moisture absorption layer is disposed on the supporter for absorbing moisture in the packaged structure. Another China Patent Application Series No. 200610082800.8, published on Dec. 6, 2006 discloses a double-sided electroluminescent display, in which a packaging adhesive is disposed between two electroluminescent components to package the double-sided electroluminescent display and absorb moisture. Another China Patent Application Series No. 200510069655.5, published on Sep. 28, 2005, discloses a double-sided electroluminescent display, in which the thickness of the whole double-sided electroluminescent display is reduced to elevate the degree of airproof and to simultaneously reduce the difficulty in connecting the double-sided electroluminescent display with a control circuit, but the bonding of leads is still performed on the substrate.
In addition, there are two main structures for organic electroluminescent light sources nowadays, as shown in FIG. 3(a) and FIG. 3(b), in which FIG. 3(a) shows a light source with bonding at one side, comprising a substrate plate 31, a luminescent region 32, a lead bonding region 33, a cathode lead region 34, and an anode lead region 35. This structure had the following three drawbacks:
1) Uniformity of luminescence is poor: For example, as for points C and D in the luminescent region 32, since the point C is further from the lead bonding region 33 than the point D, the electric resistance from the bonding region 33 to the point C is greater than that to the point D, so that the electric current density at the point C is less than that at the point D during working, and the brightness at the point C is lower than that at the point D, i.e., the luminescence of the device is not uniform. In the meantime, the commonly used auxiliary electrodes are of metal Cr, while Cr layer has a relatively high surface resistance, so that it is difficult to effectively eliminate the non-uniformity of luminescence caused by such difference of electric current density.
2) The frame of the light source is large and the proportion of effective luminescent area to substrate area is relatively small. Since electrode leads 34 and 35 of organic electroluminescent light source are made on the substrate 31, the leads occupy a certain area of the substrate so that the effective luminescent area 32 is reduced, as shown in FIG. 3(a).
3) Life of the light source is short. Currently, the bonding and packaging are usually performed on the substrate. For example, as for the bonding region 33 in FIG. 3(a), most of the electrode leads 34 and 35 are exposed to environmental air, so they may be destroyed by external force or corrosive atmosphere, and thus the life of device is influenced adversely.
FIG. 3(b) shows a structure of another light source having double-sided bonding, which comprises a substrate 36, a luminescent region 37, a bonding region 38, a cathode lead region 39, an anode lead region 40. Since the structure is formed by employing double-sided bonding, the electric currents at points E and F in the luminescent region 37 separately flow to the adjacent bonding region 38, the current direction is different from that of single-sided bonding in which current flows to one direction, so that the difference of current density at different points in the luminescent region can be reduced and the luminescent uniformity is significantly improved in comparison with that in FIG. 3(a), but the use of metal Cr auxiliary electrodes still influence the luminescent uniformity.
Due to the use of double-sided bonding, the manufacture process is complex, which may limit the application of such light source. In addition, the aforementioned drawbacks 2) and 3) are not sufficiently overcome.